The present inventions are related to systems and methods for transferring information, and more particularly to systems and methods for obtaining data from a defective medium associated with a data transfer.
Various data transfer systems have been developed including storage systems, cellular telephone systems, and radio transmission systems. In each of the systems data is transferred from a sender to a receiver via some medium. For example, in a storage system, data is sent from a sender (i.e., a write function) to a receiver (i.e., a read function) via a storage medium. The effectiveness of any transfer is impacted by any defects associated with the transfer medium. In some cases, data loss caused by defects in the transfer medium (e.g., a physical defect or noise associated therewith) can make recovery of data from the transfer medium difficult even for data received from non-defective areas or times.
Various approaches have been developed for identifying defects in a transfer medium. In such systems, the identification of a potential defect causes a resulting nullification of any data derived from a given defective area of a medium (i.e., an erasure process). By nullifying the data, errors are not allowed to propagate through later processing steps. Turning to FIG. 1, an example of a system 100 capable of nullifying data is depicted. System 100 includes a digital filter (DFIR) 115 that receives a media data input 105 and provides a filtered version of media input 105 to a detector 120. Detector 120 performs a data detection algorithm and provides an output 170 that includes both a soft output and a hard output. In addition, system 100 includes a defect detector 110 that is operable to identify a period when the medium from which media data input 105 is derived is possibly defective. When a potentially defective region is identified, an output 112 is asserted high causing a multiplexer 125 to select a nullified data set 160 to replace output 170 from detector 120. The output of multiplexer 125 is provided to an interleaver 130 that interleaves the data and provides the interleaved data to a decoder 140. Decoder 140 performs a decoding algorithm on the data and provides a data output 150. In some cases, data output 150 is de-interleaved using a de-interleaver 135 and fed back to detector 120 where it is reprocessed on a subsequent iteration. While system 100 provides for nullifying data derived from a potentially defective region of a medium thereby reducing the possibility of error propagation, it fails to obtain any data from the defective region. In some cases, this is not acceptable as data from the defective region may be highly desirable for one reason or another.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for obtaining data from potentially defective media.